Last week I posted on the very active tropical Pacific Ocean with four storms occurring simultaneously. Tropical Cyclone Pam (17P) made a devastating visit to the island nation of Vanuatu as a Category 5 (145 kts or 165 mph) cyclone and has since joined the westerlies after passing near New Zealand as a much weaker system. Currently, the majority of the region has quieted down some, but Tropical Cyclone Nathan (east of Queensland) and Tropical Storm Bavi (West Pacific) are still active, while Tropical Cyclone Olwyn dissipated after making landfall in Western Australia. Jim Kells (OPC) compiled a few animations that show the evolution of all four tropical cyclones starting on 03/08/15. The imagery is courtesy of the MTSAT-2 satellite and we are eagerly anticipating the new Himawari-8 satellite data over the next few months.

MTSAT-2 Infrared satellite animation of the four tropical cyclones developing in the tropical Pacific and Indian Oceans valid from 03/08/2015 – 03/16/2015.

MTSAT-2 Infrared (enhanced) animation similar to the previous animation.

The MJO is currently near or at a record amplification in Phase 7 and as it swung through Phase 6 to 7, a strong westerly wind burst developed near the equator, while there was enhanced upward motion or ventilation at 200 mb. This has also been coupled with a sudden drop in the Southern Oscillation Index (another ENSO indicator).

Empirical Wave Propagation forecast for the next 40 days courtesy of CPC.

According to one forecast (above), the Empirical Wave Propagation forecast shows a return of favorable tropical cyclone formation conditions (green shading) appearing in the same region from the end of March into early April (the season typically winds down in the Southern Hemisphere after April).

Finally, notice that this region is where the warmest SSTs reside in the tropical Pacific, along with the strongest warm anomalies. This is typical of a Modoki El Nino where the warmest conditions are in the Nino 3.4 region or near the Dateline. Also notice how the water near the coast of South America is colder than normal. This shows a mixed signal and makes one wonder whether El Nino conditions will be maintained or expand east with time. . .

While most of us thaw out after a rough February into the first week of March, winter weather-wise, the Southern Hemisphere is boiling with deep convection that has spawned three tropical cyclones near Australia and the South Pacific, one tropical cyclone in the West Pacific (a twin of sorts to TC Pam in the South Pacific), and an invest area near the coast of southern Brazil. There is a weak El Nino that is centered near the dateline in the West Pacific and there is currently a strong westerly wind burst associated with the current state (Phase 6 moving to 7) of the Madden-Julian Oscillation (MJO). TC Pam and TS Bavi look to have formed near this burst as part of the overall monsoon trough that straddled the equator. TC Nathan may have also formed due to the strength of the monsoon trough, while TC Olwyn formed well to the west on the other side of Australia.

I have put together some animations and a snapshot of the of the four storms near Australia and Guam.

MTSAT-2 Infrared satellite image of four concurrent tropical cyclones in the western Pacific and eastern Indian Oceans valid at 2032 UTC on 03/11/2015.

A four day animation that shows the development of TC Pam, TC Nathan, TC Olwyn, and TS Bavi valid from 03/08/15 to 03/11/15.

MTSAT-2 Infrared Satellite imagery with GLD-360 lightning strikes overlaid showing the lightning distribution (cloud-to-ground and some intra-cloud) associated with all four tropical cyclones valid from 1432 UTC on 03/10/2015 to 2032 UTC on 03/11/2015.

Finally, a new invest area has been identified near the southern coast of Brazil on the tail end of a mid-latitude storm system. This is rare, but not unprecedented as this area occasionally sees subtropical development during the Southern Hemisphere summer. The RGB Air Mass animation below shows the system still developing, but appears to be embedded in a cold core system as indicated by the orange, red, and purplish coloring. There is a significant amount of upper-level dry air that the system has to fight through, but water temperatures are slightly above normal (+0.5C), so some additional development is possible (thank you to Dr. Jeff Masters for the information).

SEVIRI RGB Air Mass animation of Invest 90Q in the South Atlantic valid on 03/11/2015.

Thanks for reading! I’ll try to follow up on these systems as they develop.

So, we have all probably noticed that it has been cold lately. Well, due to the ample snow cover over much of the U.S. at this time, the baroclinic zone is sharpening over the lower Mississippi and Ohio River Valleys this afternoon with the aid of shortwave energy coming out of a cutoff low located over the Southwest U.S. One of the Ocean Prediction Center forecasters, Tim Collins, noted the strong contrast in temperature on either side of this zone in the RGB Air Mass image from MODIS below.

MODIS RGB Air Mass image of the strong baroclinic zone valid on 03/04/15.

Note the orange and purplish coloring to the north (above) of the moisture plume (cirrus, etc). This delineates the colder, drier air advancing south and east, while to the south (below) of the clouds there is a greenish coloring that denotes warmer mid-tropospheric air associated with a ridge of high pressure aloft over the Gulf of Mexico and Southwest Atlantic.

MODIS Water Vapor image to compliment the RGB Air Mass image valid on 03/04/15.

For contrast, the above image is the ~6.7 um water vapor channel from MODIS. Notice that north of the moisture plume you can see evidence of the lower tropopause and cold air by the relative smoothing noted in the image (lighter blue coloring due to the enhancement). To the south of the moisture plume, you can see the dry air at ~400-500 mb associated with the ridge over the Gulf of Mexico.

This baroclinic zone will continue to sharpen overnight and produce a significant snowstorm for many in the central and eastern US into tomorrow.

Thanks for reading!

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